The only difference between a god and an extremely powerful inter-dimensional alien are the number of worshippers.

In Marvel Comics lore Thor and his ilk ARE THE Norse Gods because the Norsemen worshipped them as gods.

Anyone that refuses to call them gods only does so because they aren't their gods. Which is perfectly legitimate by the way. Hank Pym, for example, is a scientist and thus refers to Thor and Loki as aliens and not gods.